Welding torch and stream nozzle

ABSTRACT

The invention relates to a stream nozzle ( 13 ) for an inert gas welding torch (B). The inventive nozzle is provided with a coating (S) that adheres to at least a part of the surface of said nozzle in a material fit and consists of silver, especially galvanically mounted contact silver.

[0001] The invention relates to a welding torch as generically definedby the preamble to claim 1 and to a stream nozzle as generically definedby the preamble to claim 8.

[0002] The stream nozzle, also known as a contact nozzle, typicallycomprises electrolyte copper, or a more-wear-resistantcopper-chromium-zirconium alloy. Other variant alloys also exist, forinstance with beryllium. The task of the stream nozzle is to transmitcurrent to the electrode wire and to guide it. For good process safety,an optimal current transfer from the nozzle stock to the stream nozzleis necessary. Moreover, the stream nozzle must transmit considerableheat over the mounting region. In practice, until now, stream nozzleshave predominantly been used without surface treatment, that is, bare orbare to the copper; they are secured replaceably to the nozzle stock viaa screw connection or a plug-type connection. In welding, welding beadsor welding splashes that occur exhibit the undesired tendency to adhereto the exposed surface of the stream nozzle. This can cause adverseeffects on the flow conditions for the inert gas that glows on theoutside along the stream nozzle to the welding point. Welding splashesadhering to the end face and in the vicinity of the exit from theelectrode wire duct can hinder advancement from friction with theelectrode wire. In practice, stream nozzles are therefore known that atleast on their jacket face and end face have a metal coating, in theform of chromium- or nickel-plating. This coating is intended to provideimproved reflection of the arc radiation (reduced heat consumption) andalso to prevent the welding splashes from adhering (anti-adhesiveeffect). Not only are coatings formed by chromium- or nickel-platingexpensive; they do not meet the expectations made of them to asatisfactory extent.

[0003] In addition, whenever the coating extends into the mountingregion of the stream nozzle, current transfer problems occur; this issuspected to be because the current transfer fluctuates as a function ofthe layer thickness. In applying the coating, it is therefore necessarythat the application region intended for the current transfer be coveredas well. This is expensive.

[0004] The object of the invention is to disclose a welding torch of thetype defined at the outset, and a stream nozzle for this kind of inertgas welding torch, that makes it economically possible to achieve anoptimal anti-adhesive and reflective action. A part of the object isalso that the metal coating have no adverse influence on the currenttransfer but instead even improve the current transfer.

[0005] The stated object is attained by the characteristics of claim 1and claim 8, respectively.

[0006] Surprisingly, a silver coating leads to excellent anti-adhesionand reflective effects. Even if the silver coating is meant to extendinto the mounting region, it has no adverse effect on the currenttransfer but in fact even improves the current transfer. The heattransfer capability of a silver coating is already optimal. Applying thesilver coating can be done economically, particularly in massproduction. Since the silver coating has no adverse effect on thecurrent transfer and in fact even improves it, when the coating isapplied there is no need to cover regions of the surface that areimportant for the current transfer. This makes coating the stream nozzlesimpler.

[0007] Expediently, the coating comprises galvanically or chemicallyapplied contact silver. Contact silver can be applied with the desiredlayer thickness and good adhesion to the material comprising the contactnozzle at low equipment expense.

[0008] The coating should have an essentially uniform layer thickness,preferably between about 6 and 10 μm.

[0009] The silver coating should be uniform, at least on the jacket faceand the free end face of the stream nozzle.

[0010] However, it is especially expedient for the entire surfaces ofthe stream nozzles to be provided with the silver coating. Thissimplifies the procedure in galvanic or chemical coating of the streamnozzle considerably. The silver coating, which is also present in theregion of attachment to or contact with the nozzle stock or inner tubeof the torch as well, leads to optimal current transfer and heattransfer and makes an important contribution to process safety.

[0011] In a stream nozzle with a screw attachment for producing a screwconnection to the nozzle stock or the inner tube of the torch, the malethread of the screw attachment is also covered with the silver coating.

[0012] A stream nozzle with a plug-in attachment for producing aplug-type connection to the nozzle stock or inner tube of the torch isalso covered with the silver coating on the fitting faces,of the plug-inattachment.

[0013] Other metal spraying methods are naturally also practicable forapplying the silver coating.

[0014] Embodiments of the subject of the invention will now be describedin conjunction with the drawing, noting that the two embodiments shownare merely a non-limiting selection from among more embodiments.

[0015] Shown are:

[0016]FIG. 1, a longitudinal section through a torch head with oneembodiment of a stream nozzle; and

[0017]FIG. 2, a longitudinal section through part of a torch head, withanother embodiment of a stream nozzle.

[0018] In a torch head K of an inert gas welding torch B in FIG. 1, aninner tube 1 of the torch, on its free end, has a male thread onto whicha nozzle stock D is mounted detachably, in the embodiment shown. On anouter tube 4 of the torch, there is a seat 5 for a gas nozzle orifice 6.Between the inner tube 1 and the outer tube 4, insulators 7 areprovided, usually of nonmetal material.

[0019] The nozzle stock D, as a sleeve 8, is equipped with nozzle bores9 and a front female-thread portion 10 for screwing a stream nozzle 13into it. The stream nozzle 13, which for instance comprises electrolytecopper or a copper-chromium-zirconium alloy, is screwed with a screwattachment 2 into the female thread 10 and is thus secured replaceably.Extending through the stream nozzle 13 is an electrode wire deliveryconduit 3, which discharges at a free end face 14; the end face 14 isoptionally slightly recessed relative to the end of the orifice 6.Between where the stream nozzle 13 is mounted on the nozzle stock D andthe end face 14, there is an outer jacket region 11.

[0020] A coating S of silver is applied over the full surface andadhering by material engagement, at least to the jacket region 11 andthe end face 14. Expediently, this is a galvanically applied contactsilver. However, the coating S can also extend as far as the screwattachment 2 and even on into the duct 3.

[0021] In FIG. 2, in a further embodiment of the stream nozzle 13, aplug-type connection is provided. The stream nozzle 13 has a plug-inattachment 2′ with fitting faces 15 that fit corresponding fitting faces10′ of the nozzle stock D.

[0022] In both embodiments, the mounting of the stream nozzle 13 on thenozzle stock D is shown. It is also conceivable for the stream nozzle 13to be mounted directly on the inner tube 1, correspondingly modified, ofthe torch.

[0023] In FIG. 2, the coating S is embodied of silver, preferablygalvanically applied contact silver, in such a way that it covers theentire surface of the stream nozzle 13; that is, it covers the end face14, jacket face 11, and fitting faces 15. The layer thickness X of thecoating S is expediently between 2 and 15 μm, and preferably betweenabout 6 and 10 μm.

[0024] For applying the silver coating, a plurality of stream nozzles 13in the bare state, optionally after conventional precleaningprocesses,.are placed in a galvanic bath, until the silver coating S hasbeen applied to the desired layer thickness.

[0025] In order to improve the anti-adhesive effect of the silvercoating S at least temporarily, the possibility exists of spraying on aparting agent, typically an oily substance, which contains additiveswith which the surface of the silver coating S is passivated, whichenhances the anti-adhesion effect.

[0026] The silver coating, extending as far as the inside of themounting region of the stream nozzle 13 to the nozzle stock D or theinner tube 1 of the torch and existing over the full surface in thisregion as well, improves the current transfer in an optimal way.

1. A welding torch (8) for inert gas welding, having on its inside anozzle stock (D) on whose end portion pointing toward the welding regiona hollow stream nozzle (13) is mounted, wherein on at least a portion ofthe surface of the stream nozzle (13), a metal anti-adhesive andreflective coating is provided, characterized in that the coating (S)has silver as its main ingredient.
 2. The welding torch of claim 1,characterized in that the coating (S) comprises galvanically orchemically applied contact silver.
 3. The welding torch of claim 1 and2, characterized in that the silver or contact silver coating (S) has anessentially constant layer thickness (X) of between 2 and 15 μm,preferably between 6 and 10 μm.
 4. The welding torch of at least one ofthe foregoing claims, characterized in that the coating (S) is providedon the jacket face (11), adjacent to the region where the stream nozzle(13) is mounted on the nozzle stock (D), and on the free end face (14)of the stream nozzle (13).
 5. The welding torch of at least one of theforegoing claims, characterized in that the coating (S) is provided onthe entire surface of the stream nozzle (13).
 6. The welding torch ofclaim 5, characterized in that the stream nozzle (13) has a screwattachment (2), whose male thread also has the coating (S).
 7. Thewelding torch of at least one of claims 1-5, characterized in that thestream nozzle (13) has a plug-in attachment (2′), whose fit face (orfaces) (15) also have the coating (S).
 8. A stream nozzle (13) for aninert gas welding torch (B), which has a wire duct (3) extendinglongitudinally through from amounting point to an end face (14), andover at least a portion of its surface, it has a metal coating adheringfirmly by material engagement, characterized in that the coating (S)comprises galvanically or chemically applied contact silver.